Semiconductor laser device

ABSTRACT

A semiconductor laser device of an AlGaInP system includes a GaAs substrate and a surface of the substrate is inclined by 5 DEG  or more from a {100} plane in a &lt;011&gt; direction.

RELATED APPLICATIONS

This application is a continuation and a division of application Ser.No. 08/134,293, filed Oct. 8, 1993 U.S. Pat. No. 5,411,915, which is adivision of application Ser. No. 07/896,386, filed Jun. 10, 1992 issuedas U.S. Pat. No. 5,264,389, which is a division of application Ser. No.07/664,866 filed Apr. 11, 1991, U.S. Pat. No. 5,146,466, which is acontinuation of application Ser. No. 07/412,786, filed Sep. 26, 1989,issued as U.S. Pat. No. 5,016,252.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor laser devicesand methods of manufacturing the same and particularly it relates to animprovement of a compound semiconductor laser device which contains Al,Ga, In and P as major constituents and emitting the visible light, and amethod of manufacturing the same.

2. Description of the Background Art

A metal organic chemical vapor deposition (MOCVD) method is an effectivemethod for growing crystals of a GaInP system (or an AlGaInP system).However, many crystal defects are often observed in the crystals of theGaInP system grown by the MOCVD method. For example, when a crystallayer of the GaInP system is grown on the {100} plane of a GaAssubstrate by the MOCVD method, about 6000 crystal defects of hillocksoval in section are generated per 1 cm² on the crystal grown plane.

According to Journal of Crystal Growth, 17(1972), pp. 189-206, it isstated that the number of undesirable pyramid hillocks on the crystalgrown surface of the GaAs layer grown by the CVD method on the GaAssubstrate can be considerably decreased by using the substrate having asurface inclined by 2° to 5° from the {100} plane in the <110>direction.

In addition, according to Journal of Crystal Growth, 68(1984), pp.483-489, a semiconductor laser device of the A GaInP system manufacturedby using the MOCVD method is described.

FIG. 1 is a schematic sectional view of such a semiconductor laserdevice of the AlGaInP system. In this semiconductor laser device, onemain surface 1a of an n type GaAs substrate 1 is inclined by 2° from a{100} plane in a <110> direction. An n type GaAs buffer layer 2 of 0.7μm in thickness, an n type (Al₀.3 Ga₀₇)₀.5 In₀.5 P clad layer 3 of 4 μmin thickness, a non-doped Ga₀.5 In₀.5 P active layer 4 of 0.23 μm inthickness, a p type (Al₀.3 Ga₀.7)₀.5 In₀.5 P clad layer 5 of 1.4 μm inthickness and a p type GaAs cap layer 6 of 1.0 μm in thickness arestacked successively on the main surface 1a.

A current blocking layer 7 having a stripe-shaped opening 8 of a widthof 20 to 23 μm is formed on the cap layer 6. The cap layer 6 exposed inthe blocking layer 7 and the opening 8 is covered with a p side Au/Znelectrode layer 9 including a Zn sub layer and an Au sub layersuccessively stacked. An n side Au/Ge/Ni electrode layer 10 including aNi sub layer, a Ge sub layer and an Au sub layer successively stacked isformed on the other main surface 1b of the n type GaAs substrate 1.

Semiconductor laser devices as shown in FIG. 1 have disadvantages suchas a large variation of oscillation threshold currents between thedevices and a deteriorated yield. According to the investigationconducted by the inventors of the present invention, many hillocks wereobserved on the surface of the cap layer 6 of such a device.

More specifically, as described in Journal of Crystal Growth, 17(1972),pp. 189-204, the utilization of a surface inclined by 2° to 5° from a{100} plane of a GaAs substrate in a <110> direction is effective insuppressing hillocks in the growing process of a GaAs crystal layer bythe CVD method but it is not effective in suppressing hillocks in thegrowing process of an A GaInP system crystal layer by the MOCVD method.

FIG. 2 is a schematic sectional view showing another conventionalsemiconductor laser device. An n type (Al₀.7 Ga₀.3)₀.5 In₀.5 P cladlayer 12, a non-doped (Al_(x) Ga_(1-x))₀.5 In₀.5 P active layer 13, anda p type (Al₀.7 Ga₀.3)₀.5 In₀.5 P clad layer 14 are epitaxially grownsuccessively on an n type GaAs substrate 11 by using the MOCVD method ormolecular beam epitaxy (MBE) method or the like. Ridges of a width ofabout 5 μm are formed by etching on the p type clad layer 14.

An n type GaAs current blocking layer 15 epitaxially grown by using amask is formed on the p type clad layer 14. However, the top surfaces ofthe ridges of the p type clad layer 14 are not covered with the currentblocking layer 14. The top surfaces of the ridges of the p type cladlayer 14 and the blocking layer 15 are covered with a p type GaAs caplayer 16 epitaxially grown.

A p side electrode layer 17 of Au/Zn/Au is formed on the cap layer 16.On the other hand, an n side electrode layer 18 of AuGe/Au is formed onthe other main surface of the n type GaAs susbstrate 11.

When the Al composition ratio of the active layer 13 of thesemiconductor laser device of FIG. 2 is x=0.1, a laser beam of awavelength of 649 nm is obtained. On the other hand, a He-Ne gas laserdevice having a wavelength of 632.8 nm is used these days as a lightsource of a bar code scanner used in a measuring instrument or apoint-of-sales (POS) system using visible laser beam. However, such agas laser device has a large size and a heavy weight and it consumesmuch power. Accordingly, it is desired to use an AlGaInP systemsemiconductor laser device having a light weight and a small size withlow consumption of power in place of a He-Ne gas laser device, byreducing the wavelength of an AlGaInP system semiconductor laser device.

An AlGaInP system semiconductor laser device capable of emitting laserbeam having a shorter wavelength can be obtained by taking one of thefollowing measures:

(1) the composition ratio of Al in the active layer is increased;

(2) the active layer is formed to have a superlattice structure (seeElectronics Letters, Vol. 24, 1988, pp. 1489-1490);

(3) each of the semiconductor layers is grown at a temperature higherthan 700° C. (see Japanese Journal of Applied Physics, Vol. 27, 1988,pp. 2098-2106); or

(4) Zn is diffused in the active layer (see IEEE Journal of QuantumElectronics, QE-23, 1987, pp. 704-711).

For example, if measure (1) is used in the case of the composition ratioof Al in the active layer 13 being x=0.2, the oscillation wavelength is630 nm to 640 nm, which value is substantially equal to the wavelengthof a He-Ne laser beam. However, if the composition ratio of Al in theactive layer 13 is increased, the quality of crystals of the activelayer 13 is lowered and the oscillation threshold current is increased,making it difficult to carry out continuous operation of thesemiconductor laser device. If either of the measure (2), (3) or (4) istaken, oscillation operation of the semiconductor laser device becomesunstable, resulting in a low yield of manufacturing and a considerabledeterioration of the active layer 13, making the life of the deviceshort.

SUMMARY OF THE INVENTION

In view of the above described related art, an object of the presentinvention is to provide an AlGaInP system semiconductor laser devicehaving little variation of oscillation threshold current and a goodyield, and a method of manufacturing the same.

Another object of the present invention is an AlGaInP systemsemiconductor laser device having a long life, and a method ofmanufacturing the same.

Still another object of the present invention is to provide an AlGaInPsystem semiconductor laser device having an oscillation wavelengthsubstantially equal to a wavelength of a He-Ne gas laser beam, and amethod of manufacturing the same.

A semiconductor laser device according to an aspect of the presentinvention comprises: a GaAs substrate of a first conductivity type; abuffer layer of the first conductivity type containing Ga, In and P,formed on one main surface inclined by 5° or more from a {100} plane ofthe GaAs substrate in a <011> direction; a clad layer of the firstconductivity type containing Al, Ga, In and P, formed on the bufferlayer; an active layer containing at least Ga, In and P, formed on theclad layer of the first conductivity type; and a clad layer of a secondconductivity type containing Al, Ga, In and P, formed on the activelayer.

A semiconductor laser device according to another aspect of the presentinvention comprises an active layer further containing Al in addition toGa, In and P.

A method of manufacturing a semiconductor laser device according to afurther aspect of the present invention comprises the steps of: forminga main surface inclined by 5° or more from a {100} plane of a GaAssusbstrate of a first conductivity type in a <011> direction, forming abuffer layer of the first conductivity type containing Ga, In and P onthe main surface by MOCVD, forming a clad layer of the firstconductivity type containing Al, Ga, In and P on the buffer layer byMOCVD, forming an active layer containing at least Ga, In and P on theclad layer of the first conductivity type by MOCVD, and forming a cladlayer of a second conductivity type containing Al, Ga, In and P on theactive layer by MOCVD.

In a method of manufacturing a semiconductor laser device according to astill further aspect of the present invention, an active layer furthercontaining Al in addition to Ga, In and P is formed by MOCVD.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a conventional semiconddctor laser device.

FIG. 2 is a sectional view of another conventional semiconductor laserdevice.

FIG. 3 is a block diagram of a crystal growth apparatus used in thepresent invention.

FIG. 4 is a sectional view of a semiconductor laser device according toan embodiment of the invention.

FIG. 5A is a histogram showing oscillation threshold current insemiconductor laser devices according to the present invention, and FIG.5B is a histogram showing threshold current in semiconductor laserdevices for comparison.

FIG. 6 is graph showing photoluminescence (PL) peak energy of a Ga₀.5In₀.5 P layer formed on a main surface of a GaAs substrate in relationto the inclination angle of the main surface.

FIG. 7 is a graph showing PL peak energy of a (Al_(x) Ga_(1-x))₀.5 In₀.5P layer (1>x>0) on a Ga₀.5 In₀.5 P layer formed on a main surface of aGaAs substrate in relation to the composition (x) of Al.

FIGS. 8A and 8B are graphs showing PL light intensity distributionsconcerning PL light wavelengths in (Al₀.15 Ga₀.85)₀.5 In₀.5 P layers inthe cases in which respective main surfaces of GaAs substrates areinclined by 0° and 5° respectively from {100} planes thereof in a <011>direction.

FIG. 9 is a sectional view of a semiconductor laser device according toanother embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3, a GaAs substrate 21 is mounted on a susceptor 23 ina reaction container 22. The susceptor 23 is rotated at a speed of 8 to10 rpm while a crystal layer is being grown on the substrate 21. Waterflow tubes 24 closely fixed to the external wall of the container 22cool the container 22. A radio frequency (RF) coil 25 wound on thecontainer 22 enables the susceptor 23 to be heated. The container 22 isevacuated by a rotary pump 27 through a filter 26.

For example, a reaction gas containing trimethyl gallium (TMGa) isobtained by bubbling a solution of TMGa by H₂ gas introduced into asolution tank 28 through a mass flow controller (MFC) 30a. Similarly, asolution of trimethyl indium (TMIn) in a solution tank 29 is bubbled byH₂ gas introduced through an MFC 30b. Another reaction gas PH₃ andcarrier gas H₂ are introduced into the reaction container 22 throughMFCs 30c and 30d, respectively. Needless to say, a further desired gascan be introduced into the reaction container 22.

In the crystal growth apparatus shown in FIG. 3, the temperature of theGaAs susbstrate 22 was maintained at 640° C. The reaction gasses wereintroduced into the reaction container 22 with a flow rate ratio of PH₃gas/(TMGa gas+TMIn gas)=500. The pressure in the container 22 wasmaintained at 70 Torr and an InGaP system crystal layer of about 1.2 μmin thickness was grown on the GaAs substrate 21 by the MOCVD method. Inorder to prevent As atoms from diffusing from the substrate 21, it isdesirable to introduce arsine gas into the container 22 during a periodof heating the GaAs substrate 21 before the start of the crystal growth.

Table I shows defect concentrations (the number of hillocks per 1 cm²)measured in InGaP system crystal layers grown on GaAs substrates havingvarious plane orientations, and photoluminescences measured in the InGaPsystem crystal layers excited by argon laser (having a wavelength of5145 Å). The photoluminescences were measured at 10K.

                                      TABLE I                                     __________________________________________________________________________                             photoluminescence                                            substrate crystal                                                                              (measured at 10K)                                            plane     defect emission                                                                             half-value                                            orientation                                                                             concentration                                                                        energy (eV)                                                                          width (meV)                                   __________________________________________________________________________    embodiment                                                                            inclined by 5°                                                                   about 100                                                                            1.954  9.0                                                   from {100}                                                                    plane in <011>                                                                direction                                                             samples for                                                                           {100} plane                                                                             about 6,000                                                                          1.877  21.0                                          comparison                                                                            inclined by 2°                                                                   about 1,000                                                                          1,887  20.0                                                  from {100}                                                                    plane in <011>                                                                direction                                                                     inclined by 2°                                                                   about 4,000                                                                          1.875  15.0                                                  from {100}                                                                    plane in <011>                                                                direction                                                                     inclined by 2°                                                                   about 3,000                                                                          1.875  14.0                                                  from {001}                                                                    plane in <011>                                                                direction                                                             __________________________________________________________________________

As is evident from Table I, the defect concentration in the InGaP systemcrystal layer grown on the GaAs substrate having a surface inclined by5° from a {100} plane in a <011> direction is by far smaller than thosein the InGaP system crystal layers on the GaAs substrates havingrespective surfaces inclined by less than 5° from the respective {100}planes in the <011> direction. In addition, the narrow half-value widthof 9.0 meV in photoluminescence of the InGaP system crystal layer on theGaAs substrate having a surface inclined by 5° from the {100} plane inthe <011> direction shows a good quality of crystals.

The growing conditions of the crystal layer can be changed as required.For example, the crystal layer can be grown at a temperature in therange of 620° C. to 670° C. In addition, not only an InGaP systemcrystal layer but also an InGaAlP system crystal layer can be grown.However, the surface of the GaAs substrate needs to be inclined with anangle of 5° or more, preferably in the range of 5° to 7° from the {100}plane in the <011> direction and, otherwise, a crystal layer having asufficiently small defect concentration could not be grown.

Referring to FIG. 4, a sectional view of a semiconductor laser diodeaccording to an embodiment of the present invention is illustrated. An ntype GaAs substrate 31 having a carrier concentration of 2×10¹⁸ cm⁻³ hasa main surface 31a inclined by 5° or more, e.g., 5° from a {100} planein a <011> direction. An n type buffer layer 32, an n type clad layer33, an active layer 34, a p type clad layer 35 and a p type cap layer 36are stacked successively on the main surface 31a. Those semiconductorcrystal layers are grown at a crystal growth temperature in the range of620° C. to 670° C., e.g., 670° C. under a reduced pressure of 70 Torr bythe MOCVD method.

Table II shows various conditions of the semiconductor layers thusgrown.

                  TABLE II                                                        ______________________________________                                                         carrier            layer                                                      concentration      thickness                                         composition                                                                            (cm.sup.-3)                                                                              dopant  (μm)                                   ______________________________________                                        buffer layer 32                                                                         n-Ga.sub.05 In.sub.0.5 P                                                                 5 × 10.sup.17                                                                      Se    0.5                                     n type clad                                                                             n-(Al.sub.0.5 Ga.sub.0.5)                                                                8 × 10.sup.17                                                                      Se    1.0                                     layer 33  .sub.0.5 In.sub.0.5 P                                               active layer 34                                                                         Ga.sub.0.5 In.sub.0.5 P                                                                  --         --    0.08                                    p type clad                                                                             p-(Al.sub.0.5 Ga.sub.0.5)                                                                7 × 10.sup.17                                                                      Mg    0.8                                     layer 35  .sub.0.5 In.sub.0.5 P                                               cap layer 36                                                                            p-GaAs     5 × 10.sup.18                                                                      Mg    0.3-0.5                                 ______________________________________                                    

A current blocking layer 37 of SiO₂ is formed on the cap layer 36 bysputtering. A stripe-shaped opening 38 for passage of current is formedin the blocking layer 37 by etching. A Cr sub layer and an Au sub layerare provided successively by vacuum evaporation to cover the cap layer36 and the blocking layer 37 exposed in the opening 38, whereby a p sideAu/Cr electrode layer 39 is formed. A Cr sub layer, an Sn sub layer andan Au sub layer are provided successively by vacuum evaporation on theother main surface 31b of the substrate 31, whereby an n side Au/Sn/Crelectrode layer 40 is formed. The p side electrode layer 39 and the nside electrode layer 40 are thermally treated at 400° C., so as to be inohmic contact with the cap layer 36 and the substrate 31, respectively.

Referring to FIG. 5A, there is shown a histogram representing variationof oscillation threshold currents in 25 semiconductor laser devicesaccording to the embodiment, manufactured by using n type GaAssubstrates 31 having respective main surfaces 31a inclined by 5° fromthe {100} planes thereof in the <011> direction. The abscissa in thishistogram represents the threshold current and the ordinate representsthe number of semiconductor laser devices.

FIG. 5B, which is similar to FIG. 5A, represents variation of thresholdcurrents in 25 semiconductor laser devices for comparison, manufacturedby using n type GaAs substrates having respective main surfaces inclinedby 2° from the {100} planes thereof in the <011> direction.

As is evident from the comparison of FIGS. 5A and 5B, the variation ofthe threshold currents in the semiconductor laser devices according tothe embodiment is smaller than that in the semiconductor laser devicesfor comparison. In addition, an average threshold current in thesemiconductor laser devices according to the embodiment is smaller thanthat in the semiconductor laser devices for comparison. Thus, accordingto the present invention, the manufacturing yield of semiconductor laserdevices is improved and the life thereof becomes long.

In addition, 1000 to 10000 cm⁻² hillocks were observed in the cap layerof each of the semiconductor laser devices, while only less than about100 cm⁻² hillocks were observed in the cap layer of each of thesemiconductor laser devices according to the embodiment of the presentinvention. Accordingly, it is considered that the decrease of thevariation of the threshold currents in the semiconductor laser devicesaccording to the embodiment is achieved by the decrease of hillocks andconsequently by the improvement of the quality of crystals.

Although the semiconductor laser device using the n type GaAs substratehaving the main surface 31a inclined by 5° from the {100} plane in the<011> direction was described in the above mentioned embodiment, themain surface 31a may be inclined by 5° or more from the {100} plane inthe <011> direction and, preferably, it is inclined with an angle in therange of 5° to 7°. An angle of inclination of less than 5° could notcontribute to an improvement of the quality of crystals and, conversely,it would take much time to form a main surface of a substrate inclinedby more than 7°. Further, if the inclination angle of the substrateexceeds 7°, the threshold current of the semiconductor laser devicewould tend to be increased and therefore such angles outside the abovementioned prescribed range are not practical.

Furthermore, in order to suppress increase of the operation voltage inthe semiconductor laser diode of FIG. 4, an intermediate layer of Ga₀.5In₀.5 P may be interposed between the p type clad layer 35 and the caplayer 36.

In addition, although the oxide stripe type laser device having theblocking layer of SiO₂ was described in the above embodiment, it isclear for those skilled in the art that the present invention isapplicable to semiconductor laser devices of other various types.

In the following, a second embodiment of the present invention will bedescribed.

The inventors of the present invention found that an energy band gap ofan AlGaInP system semiconductor layer grown on a GaAs substrate changesdependent on the surface orientation of the substrate.

Referring to FIG. 6, there is shown a relation between an inclinationangle of the surface of the GaAs substrate and a PL peak energy of aGa₀.5 In₀.5 P layer grown on the surface of the substrate. The abscissain FIG. 6 represents an inclination angle of the GaAs substrate surfacefrom the {100} plane in the <011> direction, and the ordinate representsthe PL peak energy of the Ga₀.5 In₀.5 P layer. The Ga₀.5 In₀.5 P layerwas formed at 670° C. under the pressure of 70 Torr by the MOCVD method.The PL peak energy was measured at the room temperature. As is evidentfrom the graph of FIG. 6, the PL peak energy increases according to theincrease of the inclination angle of the substrate surface and, when theinclination angle is 5° or more, the PL peak energy approaches aprescribed saturation value.

Referring to FIG. 7, a relation between a composition ratio x of Al ofan (Al_(x) Ga_(1-x))₀.5 In₀.5 P layer (1>x>0) and a PL peak wavelengthis shown. The abscissa represents the composition ratio x of Al, and theordinate represents the PL peak wavelength (nm) of the (Al_(x)Ga_(1-x))₀.5 In₀.5 P layer. The surface of the GaAs substrate wasinclined by 0°, 5° or 7° from a {100} plane in a <011> direction. AGa₀.5 In₀.5 P layer was formed on the GaAs substrate and an {Al_(x)Ga_(1-x))₀.5 In₀.5 P layer was formed thereon.

FIGS. 8A and 8B show respectively PL light intensity distributionsconcerning the PL light wavelengths of the (Al₀.15 Ga₀.85)₀.5 In₀.5 Players in the cases of the GaAs substrate surfaces being inclined by 0°and 5° from the respective {100} planes thereof in the <011> direction.In each of FIGS. 8A and 8B, the abscissa represents the PL lightwavelength, and the ordinate represents the PL light intensity. The PLwas measured at the room temperature.

As is evident from FIG. 7, the change amount of the PL peak wavelengthdue to the inclination of each substrate surface is substantiallyconstant independent of the Al composition ratio x. For example, asshown in FIGS. 8A and 8B, if the Al composition ratio is x=0.15, the PLpeak wavelengths in the cases of the inclination angles of the substratesurfaces being 0° and 5° are 642.2 nm and 622.0 nm, respectively, andthe change amount of the wavelengths in both cases is about 20 nm. ThePL peak wavelength of the (Al_(x) Ga_(1-x))₀.5 In₀.5 P layer tended to aprescribed saturation value with the inclination angle of the substratesurface being in the range of 5° or more, in the same manner as in thecase of the Ga₀.5 In₀.5 P layer shown in FIG. 6.

Based in the above described investigation by the inventors of thepresent invention, it was found that it is possible to shorten awavelength of a laser beam by inclining the substrate surface from the{100} plane in the <011> direction in an AlGaInP system semiconductorlaser device. However, the inclination angle of the substrate surface isselected to be 5° or more, preferably, in the range of 5° to 7°. This isbecause a sufficiently short wavelength of laser beam can be obtainedeven if the Al composition ratio x is small in the case of theinclination angle of the substrate surface being 5° or more and thenumber of hillocks in the semiconductor layer can be decreased to 100cm⁻² or less.

Referring to FIG. 9, a semiconductor laser device according to thesecond embodiment of the invention is shown. Table III shows variousconditions of the semiconductor layers included in this semiconductorlaser device.

                  TABLE III                                                       ______________________________________                                                         carrier            layer                                                      concentration      thickness                                         composition                                                                            (cm.sup.-3)                                                                              dopant  (μm)                                   ______________________________________                                        buffer layer 32                                                                         Ga .sub.0.5 In.sub.0.5 P                                                                 5 × 10.sup.17                                                                      Se    0.5                                     n type clad                                                                             (Al.sub.0.7 Ga.sub.0.3)                                                                  8 × 10.sup.17                                                                      Se    1.0                                     layer 43  .sub.0.5 In.sub.0.5 P                                               active layer 44                                                                         (Al.sub.0.15 Ga.sub.0.85)                                                                --         --    0.08                                              In.sub.0.5 P                                                        p type clad                                                                             (Al.sub.0.7 Ga.sub.0.3)                                                                  7 × 10.sup.17                                                                      Mg    0.8                                     layer 45  .sub.0.5 In.sub.0.5 P                                               cap layer 36                                                                            GaAs       5 × 10.sup.18                                                                      Mg    0.3-0.5                                 ______________________________________                                    

The semiconductor laser device in FIG. 9 is similar to that in FIG. 4,except that only the compositions of the n type clad layer 43, theactive layer 44 and the p type clad layer 45 are changed. Accordingly,the device in FIG. 9 is manufactured by the same process as that in FIG.4.

Although the semiconductor laser device including the active layer 44having the AL composition ratio of x=0.15 was described in connectionwith the second embodiment, those skilled in the art will easilyunderstand that Al composition ratio x can be changed in order to obtaina laser beam having a desired wavelength. For example, in order toobtain a wavelength of about 630 nm approximate to the wavelength of theHe-Ne gas laser beam, the Al composition ratio x of the active layer 44can be selected to be in the range of 0.1 to 0.15 with the inclinationangle of the substrate surface 31a being 5° or more.

In the semiconductor laser device in FIG. 9, the Al composition ratiofor obtaining a laser beam of a short wavelength can be made shallcompared with the conventional devices and accordingly increase of thethreshold current can be suppressed. In addition, since the number ofcrystal defects in each semiconductor layer is small, there is lessvariation of the threshold current and the life of the device isincreased.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. In a semiconductor laser device comprising:a GaAssubstrate of a first conductivity type having a main surface inclined byat least about 5° from a {100} plane of said substrate in a <011>direction, a first clad layer of a first conductivity type containingAl, Ga, In and P, formed on said main surface, an active layercontaining Ga, In and P, formed on said first clad layer, a second cladlayer of a second conductivity type containing Al, Ga, In and P, formedon said active layer, an intermediate layer formed on said second cladlayer, and a GaAs cap layer of the second conductivity type formed onsaid intermediate layer.
 2. The device of claim 1, further comprising abuffer layer of the first conductivity type formed between said mainsurface and said first clad layer.
 3. The device of claim 1, whereinsaid main surface is inclined in the range of from about 5° to about 7°from the {011} plane in the <011> direction.
 4. The device of claim 1,wherein said active layer further contains Al.
 5. The device of claim 4,wherein said first and second clad layers and said active layer have acomposition of (Al_(x) Ga_(1-x))₀.5 In₀.5 P, the values of x in saidfirst and second clad layers being greater than in said active layer. 6.The device of claim 5, wherein the value of x in said active layer is inthe range of from about 0.1 to about 0.15.
 7. The device of claim 5,wherein said buffer layer contains Ga, In and P.
 8. The device of claim1, wherein said intermediate layer contains Ga, In and P.
 9. The deviceof claim 8, wherein said intermediate layer has a composition of Ga₀.5In₀.5 P.
 10. The device of claim 1, further comprising a currentblocking layer of SiO₂ formed on said cap layer, said blocking layerhaving a stripe-shaped opening for enabling passage of current.
 11. In asemiconductor laser device comprising:a GaAs substrate of a firstconductivity type having a main surface inclined by at least about 5°from a {100} plane of said substrate in a <011> direction, a first cladlayer of a first conductivity type containing Al, Ga, In and P, formedon said main surface, an active layer containing Ga, In and P, formed onsaid first clad layer, a second clad layer of a second conductivity typecontaining Al, Ga, In and P, formed on said active layer, anintermediate layer formed on said second clad layer, and a GaAs caplayer of the second conductivity type formed on said intermediate layer,whereby a main wavelength of light emitted from said semiconductor laserdevice is shorter than that of light emitted from a semiconductor laserdevice including a GaAs substrate having a main surface of a {100}plane.
 12. The device of claim 11, further comprising a buffer layerformed between said main surface and said first clad layer.
 13. The,device of claim 11, wherein said active layer further contains Al. 14.The device of claim 11 wherein said main surface is inclined in therange of from about 5° to about 7° from the {100} plane in the <011>direction.
 15. The device of claim 11, wherein said intermediate layercontains Ga, In and P.
 16. The device of claim 15, wherein saidintermediate layer has a composition of Ga₀.5 In₀.5 P.
 17. In asemiconductor light emitting device comprising:a GaAs substrate of afirst conductivity type having a main surface inclined by at least about5° from a {100} plane of said substrate in a <011> direction, a firstclad layer of a first conductivity type containing Al, Ga, In and P,formed on said main surface, an active layer containing Ga, In and P,formed on said first clad layer, a second clad layer of a secondconductivity type containing Al, Ga, In and P, formed on said activelayer, an intermediate layer formed on said second clad layer, and aGaAs cap layer of the second conductivity type formed on saidintermediate layer.
 18. The device of claim 17, further comprising abuffer layer of the first conductivity type formed between said mainsurface and said first clad layer.
 19. The device of claim 17, whereinsaid active layer further contains Al.
 20. The device of claim 17wherein said main surface is inclined in the range of from about 5° toabout 7° from the {100} plane in the <011> direction.
 21. The device ofclaim 17, wherein said intermediate layer contains Ga, In and P.
 22. Thedevice of claim 21, wherein said intermediate layer has a composition ofGa₀.5 In₀.5 P.
 23. In a semiconductor light emitting device comprising:aGaAs substrate of a first conductivity type having a main surfaceinclined by at least about 5° from a {100} plane of said substrate in a<011> direction, a clad layer of a first conductivity type containingAl, Ga, In and P, formed on said main surface, an active layercontaining Ga, In and P, formed on said first clad layer, a second cladlayer of a second conductivity type containing Al, Ga, In and P, formedon said active layer, an intermediate layer formed on said second cladlayer, a GaAs cap layer of the second conductivity type formed on saidintermediate layer, and whereby a main wavelength of light emitted fromsaid semiconductor light emitting device is shorter than that of lightemitted from a semiconductor light emitting device including a GaAssubstrate having a main surface of a {100} plane.
 24. The device ofclaim 23, further comprising a buffer layer formed between said mainsurface and said first clad layer.
 25. The device of claim 23, whereinsaid active layer further contains Al.
 26. The device of claim 23,wherein said main surface is inclined in the range of from about 5°, toabout 7° from the {100} plane in the <011> direction.
 27. The device ofclaim 23, wherein said intermediate layer contains Ga, In and P.
 28. Thedevice of claim 27, wherein said intermediate layer has a composition ofGa₀.5 In₀.5 P.